I'll have a go, but don't know if these are the answers they are after...
2. Earth fault loop impedance too high to be sure fault current protective
device will operate within the required time (or even at all) on a short
circuit to earth (EEBAD).
3. Protection of an IT system against earth faults (where earth fault loop
impedance is deliberately high).
IIRC, the standard answer is:
Typically fitted where there is little or no risk of
accidental direct contact and hence no need for protection
against electric shock - but there is a high risk of fire,
particularly in the event of malfunction. Or where the
nature of the load can produce high transient imbalance
currents on state change.
Thus, fitted to protect fixed, high level stage and theatre
lighting, agricultural buildings, industrial buildings with
remote operation of plant.
ISTR that they are also used to protect long service cables
where there is a risk of fire.
I may be wrong on the above, but, hopefully, at least it may
give you directions to look. I get mixed up between the
rules for 300mA and 500mA devices....and would look it up,
if I had to actually use one.
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